Electronic devices, such as mobile phones and tablet computers usually include a direct current (DC) power conversion circuit. A common DC power conversion circuit includes a DC power source chip and a protection circuit. The DC power source chip includes an enable pin and an output pin, converts a voltage to a suitable voltage and powers electronic components of the electronic device via the output pin. The protection circuit is connected between the output pin and the enable pin of the DC power source chip. When the voltage of the output pin is greater than a permitted value, the protection circuit would output a signal to the enable pin of the DC power source chip causing the DC power source chip to stop working. However, when the DC power source chip is damaged, the DC power source chip remains to output the voltage via the output pin although the enable pin receives the signal from the protection circuit.